Yes. How you measure your flour can make a big difference. I just did a test.
I dipped a scoop of flour straight from the canister, and it weighed 4.5 ounces.
Then I stirred my flour to lighten it, and dipped. It weighed 4.25 ounces.
Then I gently spooned the flour into the scoop, and it weighed 4 ounces.
Then I sifted it first, then spooned it, and it weighed 3.5 ounces.
Those are some big differences. And different recipes are based on different methods.
As for sifting, if the recipe says, "1 cup of sifted flour", you sift first then measure. If it says, "1 cup of flour, sifted", you measure first then sift.
Like you, I live on the Gulf coast, so we have some humidity. It's warm enough here that my windows are open. All of these things make a difference in the measurement of the flour. My test above was done with KA all-purpose flour. If I had used cake flour, it all would have been lighter.
Too much flour is one thing that can make a cake dense, which is why you have to be consistent. The usual method is to stir up your flour to unpack any settling, then spoon it into the measuring cup. Use a knife to level it off.
But the best way is to get a scale and weigh it.